Resistor arrays are used for a variety of applications including digital potentiometers. Such arrays may be generated from discrete resistors or from commercially available integrated circuits including a plurality of resistors. The resistors are typically coupled with electrical relays or switches, such as dual in-line package (DIP) switches, to provide a selectable range of resistance values. Furthermore, controllable switches rather than manual switches may be utilized to provide control over the selection of the resistor values to a processor or other control device, typically digitally. Such a digital potentiometer may be useful, for example, in instrument setup, tuning, calibration or wherever a resistor value needs to be changed remotely in a circuit. However, combining metal to metal contact switches with discrete resistors, while generally providing high isolation and low insertion losses, typically requires significant circuit board space as compared with integrated circuit type devices.
Microelectromechanical systems (MEMS) have been developed as alternatives to conventional electromechanical devices, such as relays, actuators, valves and sensors. MEMS devices are potentially low-cost devices, due to the use of microelectronic fabrication techniques. New functionality also may be provided, because MEMS devices can be much smaller than conventional electromechanical devices.
It has been proposed to utilize particular MEMS devices integrated with a variety of other electrical components. U.S. Pat. No. 5,880,921 to Tham et al. is directed to a monolithically integrated switched capacitor bank using MEMS technology. U.S. Pat. No. 5,834,975 to Bartlett et al. discusses an integrated, variable gain microwave frequency power amplifier which includes a number of individual amplifier stages having outputs connected to MEMS switches. U.S. Pat. No. 5,872,489 to Chang et al. is directed to an integrated, tunable inductance network with a number of fixed inductors fabricated on a common substrate along with a switching network including MEMS switches. Similarly, it is known to provide a resistor array in combination with MEMS switches. Notwithstanding the above-described advances and suggestions, there continues to be a need for selectable resistor networks having a small footprint and suited to large scale production.